Molecular and Biochemical Aspects of Selenium Deficiency

Abstract

Selenium deficiency results in a decrease in both cellular and plasma glutathione peroxidase activities. This decrease was found to occur in a number of individuals receiving intravenous hyperalimentation. With selenium replacement, there was a rapid increase in plasma glutathione peroxidase activity and a much slower increase in red blood cell glutathione peroxidase activity. Using polyclonal antibodies to cellular glutathione peroxidase, it was found that all of the glutathione peroxidase activity in red blood cells was due to the selenium-dependent glutathione peroxidase protein and that with selenium deficiency there was an absence of both activity and protein. With selenium replacement, there was a one to one correspondence in the appearance of activity and protein. Plasma glutathione peroxidase was not immunoprecipitated by antibodies against the cellular enzyme. Antibodies were prepared against purified plasma glutathione peroxidase and these did not cross-react with the cellular enzyme. In the absence of selenium, both the plasma glutathione peroxidase activity and protein were diminished. Using these mutually non-cross reactive antibodies, it was determined that the liver cell line, Hep G2, like other cells, synthesized the cellular enzyme. In addition, however, this cell synthesized and secreted the plasma enzyme. The activity of cellular glutathione peroxidase in this liver cell line could be enhanced three-fold by the addition of exogenous selenium.